The present invention relates to disc drive data storage devices and, more particularly to a disc drive having a slider with surface discontinuities for preventing migration of disc lubrication or contaminants to the air bearing surfaces.
Disc drives of the "Winchester" type are well known in the industry. Such drives use rigid discs coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective head gimbal assemblies (HGAs). HGAs carry transducers which write information to and read information from the disc surface. An actuator mechanism moves the head gimbal assemblies from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each head gimbal assembly. The suspension provides a preload force which urges the head gimbal assembly toward the disc surface.
The head gimbal assembly includes a hydrodynamic (e.g. self generatic air) bearing the slider and a gimbal. The gimbal is positioned between the suspension and the slider to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc. Alternatively, the gimbal has been integrated within the suspension.
A conventional catamaran slider includes a pair of raised side rails which face the disc surface and form air bearing surfaces. As the disc rotates, the disc drags air under the slider along the air bearing surfaces in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the side rails, skin friction on the air bearing surfaces causes the air pressure between the disc and the air bearing surfaces to increase which creates a hydrodynamic lifting force that causes the slider to lift and fly above the disc surface. The preload force supplied by the suspension counteracts the hydrodynamic lifting force. The preload force and the hydrodynamic lifting force reach an equilibrium based upon the hydrodynamic properties of the slider and the speed of rotation of the disc. A self-loading slider further includes a cross rail which extends between the side rails. Air passing over the cross rail expands creating a subambient pressure area which forces the slider closer to the disc surface.
A typical magnetic disc is coated with a thin layer of perfluoronated lubricant for reducing wear at the head and disc interface. While most of the lubricant remains bonded to the surface of the disc, a small portion of the lubricant remains free and tends to collect on the slider surface. When the disc stops rotating and the slider rests on the disc surface, it has been observed in the development of the present invention that the collected lubricant tends to migrate to the air bearing surfaces where the collected lubricant tends to pull the slider and the disc surface together by the action of meniscus surface tension. The force by which the slider and the disc surface are pulled together is known as "stiction". The stiction force adversely affects contact start and stop (CSS) performance of the slider and may be high enough to prevent the spindle motor from rotating the disc.
One method of reducing the stiction and improving CSS performance is to lap a crown onto the air bearing surface by pressing the slider against a spherically shaped lapping plate. A crowned air bearing surface reduces collection of lubrication between the slider and the disc. However, more complete solutions to reducing stiction are desired.